Abstract
Most collision avoidance strategies for highway vehicles have primarily been based on control of 1 degree-of-freedom (1 DOF). Such collision avoidance strategies typically use RADAR or other range sensors as a means to servo on the distance between the controlled vehicle and the vehicle in front. However, for large inertia vehicles such as trucks, such strategies which involve engine/transmission or brake control, may likely prove inadequate for avoiding collisions with vehicles on either side or with animals. A 2 DOF strategy involving both steering and speed control conceptually offers significant advantages over 1 DOF strategies. A 2 DOF strategy is introduced that is based on the concept of a virtual bumper. As the name implies, the approach is based on surrounding the perimeter of the vehicle with a sensor-based computer controlled `bumper'. As the bumper's boundary is `deflected,' (i.e. the vehicle's `personal space' is invaded) a virtual force proportional to the amount of deflection is generated. The vehicle controller responds to this virtual force in such a way as to return the bumper to its non-deflected state. Information on the road geometry can also be used to generate a virtual force field to keep the vehicle in its lane. A number of vehicle mounted RADAR units measure the range and range rate between the sensors (mounted and oriented to cover the field around the vehicle) and the obstacle. Using this sensory information and an impedance based control algorithm, the vehicle will attempt to always move away from the obstacle in a controlled manner using both steering and speed control. By integrating local lane/shoulder information and sensor provided data on incursions into the vehicle's personal space, appropriate trajectory displacements are generated based on the virtual force summation. In this paper, we discuss a number of issues that need to be addressed in developing such virtual bumpers.